Low temperature liquid concentration



July 23, 1957 c. BERGER 2,800,000

LOW TEMPERATURE LQUID CONCENTRATION Filed July 27. 1953 23 il: |5 Il 25 I l f I n Y 33 7 s P f- -T- 4| .v/I/ ,f l f/ REFmGERA-nop 43 45 /7 SYSTEM y// ^47 y fllllll'lllllll TIIIIIII.' g

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- CARL BERGER 4 BY ev enmm, T

United States Patent' LOW TEMPERATURE LIQUID' CONCENTRATON Carl Berger,l Dag/tom Ghia, assigner to The Commonwealth EngineeringV Company of'thio, Dayton', Ghio, a corporation of Ohio Application July 27, 1953, Serial No. 370,534

2 Claims. (Ci. 62l24) This invention relates .to a method of concentrating liquid-bearing substances and to apparatus therefor.`

The concentration of solutions by the slow freezing of the solvent from the solution is known; efficient processes and apparatus for eecting the same are described in United States Patents 2,552,525 and 2,559,205 to- E. P. Wenzelberger, for example.

lt is a primary object of this inventionV to describe` an improved process for the low temperature concentration of liquid-bearing substances.

It is an important object of this invention to describe a system for low temperature concentrationV of liquid-bearing substances which system requires only veryy simple apparatus.

The attainment of these and other allied objectives may be exemplified in the case of a solution, for example, by effecting within the solution a slow continuous growth ofV small crystals of the solvent material; the growth of these crystals in accordance with the invention is achieved by contacting the solution with a solidified body ofthe solvent and then withdrawing heat from the solution through the said solidified body.

The withdrawal of the heat in the described manner causes that portion of the solution in contact withv the solidified body to be the lowest in temperature; accordingly crystal formation occurs at the interface between the solution and the solidified body and the body slowly increases in size as the small crystals form and accumulate; the deposition of the crystals removes solvent from the solution thereby effecting the concentration thereof.

The refrigeration or heat withdrawal is readily controlled and the rate of cooling is such that very tiny crystals form on the solidified body to build it up in substantially a layer-like manner. This avoids entrapment of the mother liquor which itself freezes at a lower temperature and is apparently squeezed away from between the solidified body and the solidifying solvent as growth proceeds. In effect then an advancing front of a solidified body occasions a diminution in the volume of solution while increasing the concentration of the solute therein.

Different solutions will of cource have different. equilibrium freezing pointsthat is-temperature at which the solution as a whole freezes and at which the liquid and solid solvent are in equilibrium. Accordingly for optimum conditions of cooling the cooling rate is varied depending upon the equilibrium freezingpoint. Cooling of the whole of the solution to the equilibrium point is to be avoided; if the cooling is sufficiently slow however the diluent or solvent separates out in solid form as the equilibrium point is approached-thus forming of itself a solution of different concentration having a different and lower equilibrium freezing point. Further it may be noted that since solid diluent and liquid diluent are always in contact no super-cooling occurs; thus in the process of invention no tendency to freeze to a completely solidmass is present.

The apparatus of invention preferably comprisesV a single tank having the base thereof cooled from the outer lCC side while the solidified mass of diluent is adjacent the base of the inner side, The base is most suitably ofV a very heat-conductive metal such as aluminum or copper al'- though the choice of material may vary with the nature of the material to be concentrated. Stainless steel, for example, is preferred for many weakly acid solutions.

The walls of the tank as well as the top are suitably equipped with inlets and outlets as will be more particularly noted hereinafter and are preferably adapted to resist the passage of heat therethrough-thus heat transfer from the liquid in the tank will be substantially solely through the bottom wall and? the solidified solvent mass.

The shape of the tank is of some importance as" the heat transfer conditions must be such that the surface'of the solid diluent exposed to the liquid diluent is always colder than any pointv in the liquidV diluent itself; this prevents solidy formation other than at? the surface ofthe solid. Further there is a tendency for crystal growth to begin at theV periphery of the'- solid diluent where it abuts the container walls; accordingly it is frequently desirable to taper the container4 walls inwardly as this inhibits treeing and assists in the attainment of uniform growth of the solid diluent across the face thereof.

The material of the container walls mayv influence the temperature point at which crystallization is initiated and may be readily selected of plastic, metal or glass to control the same in desired fashion.

The invention will be more fully understood by reference tothe following detailed' description and accompanying drawing wherein:

Figure l' illustrates one embodiment of apparatus'useful in the practice of the invention;

Figure 2 illustrates one arrangement of heat transfer apparatus useful in a structure such as that shown in Figure l;

Figure 3l is another `arrzmgement of heat transfer apparatus;

Figure 4l is another arrangement of heat transfer apparat-us in which the coolant directly contacts a heat transfer plate; and

Figure 5 illustrates one form Iof bottom wall useful in the structure of Figure l.

Referring to the drawing there is shown at 1 a tank in the form of an inverted frustum of a cone having an interior chamber 3, 'a bottom wall 5, yside walls 7', 9 anda top 11 which is preferably a continuation of the side walls.

The top l1 is centrally provided with a shaft 13 mounted for rotation in bearings 15 and carrying at the lower end thereof a stirrer blade i7. The other end of the shaft is suitably connected to a driving motor 19 for effecting stirrer blade operation when desired; the stirrer if employed need only extend' slightly below the solution surface as it is employed merely to prevent freezing in the -upper body of the solution.

Also extending through top 1l is a conduit 21 provided with a valve 23 for the passage of liquids to be concentrated. A valve 2S disposed on the opposite side of the tank top 11 is adapted to automatically control the air pressure within chamber 3.

The side walls 7 9 are each of metal Iand conduits. 27, 29, 31, 33, 35, 37 pass through each of the walls and each conduit is valved to permit passage of liquid when desired. The conduits are preferably sealed in air-tight relation to the walls as are the conduit 21, valve 25 and shaft 13, `and accordingly the spacing 39 may be evacuated to provide against undue heat transmission through the walls. While not normally required the auxiliary apparatus may be heat insulated with respect to the walls to further diminish heat transfer.

The bottom wall 5 is of aluminum and the lower face thereof intimately abuts the upper face 41 of a suitable g v r3 refrigeration system 43. This refrigeration system is in no way critical land accordingly is not shown in detail since any of the customary refrigeration apparatus known to the 'art,.such,as` the usual coils carrying a refrigeratedy medium, may b'e employed, and such will normally be selected in accordance with space and temperature conditions of the system.

The bottom 5 is itself supportedon an insulation body 43 which is preferably a ring of rubber or `similar material vulcanized Yto the bottom wall 5 and to the walls 7, 9.

Secured to the lower face of ringe-43 are suitably spaced supporting members as at 45, 4,7 which maintain the whole unit above floor level. l

-As shown in the figure the tank is partially filled with orange juice to just `above the level'49 'and is in contact .with a block of ice 5l supported on the bottom 5. The ice 51 is first preferably formed by placing a small quan'- tity of water into the tank and freezing the same by with- Y drawing heat through bottom 5 by means of the refrigeration system. The valves 31, 37 are of ycourse closed at this time.

The orange juice is then admitted (with valves 27, 29,

`is also above the ice temperature.

The refrigeration system preferably continues to oper- V.ate during the admissionV of the juice and since substantially no heat transfer occurs through the lateral walls the coldestV juice at any given time will be that in contact with the ice. Accordingly ice crystal formation begins usually at the juncture of the ice and the solution; the sloping side ofV wall 9 inhibits treeing and the ice formation takes place in substantially flat thin layers as indicated by the Y dotted line 53.

Y Control of this layer formation for various solutions may be exercised by varying the shape of the walls, the area of contact of bottom wall 5 with the refrigerating Vplate 41 or more suitably by varying the cross-sectional shape or material of plate or wall 5. Y Y f Thus as shown in Figure 2 the refrigeration system may ycomprise an upper layer 6l of aluminum, a layer 63 of nickel and the cooling coils 65 for the passage `of refrigerant. In this instance the layer 51 in the refrigeration system wouldV be placed directly against bottom wall 5 and the net ef'ect'would be to decrease the heat transfer capacity over that of simply a thin aluminum wall.

Figure 3 illustrates an arrangement in which a layer 67 of 'aluminum is contacted by small granules ofy finely divided copper 71 in which are embedded the cooling coils 69 supported by va, metallic (aluminum) closure member 73. Y The finely divided copper assists in attaining a very uniform overall'temperature condition at the layer 67 which contacts the bottom wall 5 of the tank.

Y33 and Y35 also closed) through the conduit 21 and valve Figure 4 illustrates an 'arrangement in which a liquid i coolantis fiowed through an inlet 77 to contact plate 75 Vin the spacing 81, the liquid exiting through outlet 79.

Y' control is effective since the original layer of solid solvent l 'will be greater at Vthe center than at the thus decreasing heat transfer through the center. Alternatively if desired the bottom wall may be convex or the thickness of the material in the wall and the nature of the material may 4be varied toV control heatwithdrawal from the solution.

As the withdrawal of heat proceeds (referring again f to Figure l) the body of ice increases in thickness incrementally and simultaneously the juice is concentrated. The concentration may proceed to any desired extent, as

for example, to the point at which the top of the ice is just below the aligned conduits 29, 35 when the refrigeration apparatus is shut off. The valves of these conduits 29, 35 may then be opened and the concentrated liquid drained from the chamber.

When drainage has been completed and with the valves 29, 35 again closed steam may be introduced through inlet valve 55 to the spacing 39 and circulated to cause a melting or partial melting of the ice mass. If complete melting is desired the Water may be drained off through valves (not shown)V to completely empty the chamber. If partial melting is desired valves 31, 37 may be utilized to draw oft" the solvent.

Y In given instances it may be desirable to concentrate the juice to a further degree, for example, until the ice mass is just below valves 27, 33. After withdrawal of the concentrated juice the ice may then only be partially melted, that is to the level of valves 29, 35 whereupon the water may be drawn oif to waste through these latter valves. The ice remaining may then serve as the base for a further concentration process in the same manner as hereinbefore described.

Ordinarily in the freezing process the natural heat diffusion currentsV which arise as heat is withdrawn are suicient to circulate the liquid over the ice mass. In such case the -stirrer blade 17 is not operated. In the event'however that a particular material does not circulate readily,Y or when the concentrate becomes viscous, the s tirrer may be slowly operated to cause slow movement of the liquid. Y

The'process and apparatus while described with particu lar reference to a fruit juice is readily applicable to organic solutions such as pyridine in acetophenine and so forth; the solvent need not be water and various adaptations of the apparatus described may be made to permit of very low temperature operation.

It will be understood that thisinvention is susceptible to modification in order to adopt it to different usages and conditions and accordingly, it is desired to comprehend such modifications within this invention as may Afall within the scope ofthe appended claims.

I claim: p j y1..,Ina11paratus for freeze concentration of materials a tank having a heat conductive bottom wall and up- 'wardly inwardly tapering side walls, means insulating the interior of the'tank from the atmosphere along the side walls, means cooperable with-the bottom wall of the tank for withdrawing heat from the tank through the bottom wall thereof, a plurality of drain conduits in vertical relation extending from the tank to the exterior, and inlet conduit means for the entry to the tank of material to be concentrated, the bottom wall of the tank being adapted to support a volume of` liquid interiorly of the tank.

2. VA method of concentrating a liquid bearing material comprising a diluent by freezing out of the diluent which comprises the steps of retainingV arsmall quantity of the diluentron a horizontal surface and freezing the same to a solidrmass, maintaining the solid mass of diluent frozen and confining a relatively large volume of the liquid bearing material on top of the solidified mass of the diluent above the interface surface portion thereof, withdrawing heat Vfrom the liquid bearing material substantially only through the solid mass of diluent while maintaining the temperature of the body of liquid bearing material above its solidication point, stirring the liquid bearing material adjacent thesurface of the material but remote from the interface, lowering the temperature of the liquid bearing whereby the material is concentrated, and thereafter. with- Y drawing the concentrated liquid bearing material from the solidified diluent.

References Cited in the le of this patent UNITED STATES PATENTS 5 Church Nov. 13, 1894 Church Nov. 13, 1894 Murphy Jan. 12, 1897 Monti Apr. 27, 1909 Johnson Mar. 9, 1926 10 Schulse Nov. 2, 1937 6 Paul Sept. 10, 1940 Wussow et a1 Nov. 12, 1940 Dalton Ian. 6, 1942 Ax et al Apr. 6, 1943 Majonnier June 1, 1943 Whitney Feb. 1, 1944 Pfetcher May 17, 1949 Reedall May 5, 1953 FOREIGN PATENTS Great Britain July 23, 1929 

1. IN APPARATUS FOR FREEZE CONCENTRATION OF MATERIALS A TANK HAVING A HEAT CONDUCTIVE BOTTOM WALL AND UPWARDLY INWARDLY TAPERING SIDE WALLS, MEANS INSULATING THE INTERIOR OF THE TANK FROM THE ATMOSPHERE ALONG THE SIDE WALLS, MEANS COOPERABLE WITH THE BOTTOM WALL OF THE TANK FOR WITHDRAWING HEAT FROM THE TANK THROUGH THE BOTTOM WALL THEREOF, APLURALITY OF DRAIN CONDUITS IN VERTICAL RELATION EXTENDING FROM THE TANK TO THE EXTERIOR, AND INLET CONDUIT MEANS FOR THE ENTRY TO THE TANK OF MATERIAL TO BE CONCENTRATED, THE BOTTOM WALL OF THE TANK BEING ADAPTED TO SUPPORT A COLUME OF LIZUID INTERIORLY OF THE TANK. 